Effluent cleaning device

摘要

EFFLUENT CLEANING DEVICE USING FLOCCULANT OF PREF ACRYLIC OR METHACRYLIC ACID COPOLYMER... Separation of solid particles from their mixture with a liquid carrier in which the mixture together with a synthetic flocculating agent with a m.wt. in excess of 500,000 is passed into a vertical frustro-conical vessel with the wide end at the top, by which the mixture is allowed to separate into a clear upper layer and a lower layer of coagulum which is stirred in the lower half of the vessel, from the base of which solids are removed, while clear liquid is discharged from the top. The process is continuous and the quantity of flocculant - pref. a copolymer of acrylic or methacrylic acid - added, is 0.09-13.6 kg/ton treated solids (dry basis). The stirrer is designed to move the coagulum without significantly disturbing the clear liquid above it and to rotate at not more than 5 r.p.m. so that no part of it has a linear speed exceeding 6 m/min. and pref. all parts have linear speeds within the range 0.9-2.1 m/min. Advantageously, the flocculating agent is added to the entering effluent in a pre-treatment drum of dimensions and rotary speed such that a retention time of at least 20 secs. is provided but without deposition of solids in the drum, the treated liquid leaving the drum then passing directly into the settling vessel. Arrangements can be made for automatically opening the sludge valve whenever a suitable quantity has been accumulated in the base of the settling vessel. The process can be used in the treatment of effluent from coal washings, sand and gravel plants, paperworks, etc.